Turbochargers are incorporated into engines to increase the engine's power to weight ratio. It may be desirable to adjust the flowpath of the exhaust gas into the turbine to facilitate adjustment of the turbine's characteristics based on the engine operating conditions. For example, twin scroll turbines have been developed to achieve adjustment of the turbine's characteristics. A twin scroll turbine may include two scrolls for delivering exhaust gas to the turbine rotor and a valve configured to adjust the flow-rate of the exhaust gas through the scrolls. The geometry of each of the scrolls may be designed to decreases loses over a variety of engine operating conditions. For example, the first scroll may be sharply angled for a quicker response during lower engine speeds and a second scroll may be less angled to decrease losses during higher engine speeds.
In some twin scroll turbines, an adjustment mechanism may be provided in the turbine housing which enable adjustment of the exhaust gas flowrate through each of the scrolls. U.S. Pat. No. 5,855,117 discloses a turbine housing having two inlet flow passages and an adjustment apparatus integrated into the housing configured to adjust the flowrate from both of the inlet flow passages to the turbine rotor. The Inventors have recognized several drawbacks with this type of design. Various components in the adjustment mechanism, such as the axial slide member, may be prone to thermal degradation due to the high temperatures experienced in the inlets. Moreover, the tolerance required for the axial slide member may not be achievable within cost targets. Consequently, the losses in the turbine may be increased.
As such in one approach, a turbocharger is provided. The turbocharger includes a housing and an adjustable core at least partially circumferentially surrounded by the housing, the adjustable core having a turbine rotor coupled to a compressor rotor via a shaft. The turbocharger further includes an adjustment mechanism coupled to the adjustable core configured to adjust an axial position of the housing relative to the adjustable core in response to adjustment commands.
When the turbocharger is structured in this way, the adjustment mechanism may be spaced further away from the high temperature exhaust gas. As a result, the likelihood of thermal degradation of the adjustment mechanism may be reduced, and more reasonable tolerances can be specified. Therefore, adjustability of the exhaust flow-rate through a turbine scroll is achieved while reducing the likelihood of thermal degradation of the adjustment mechanism, and meeting cost targets.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. For example, while the examples provided herein show axial displacement of the core, rotational displacement (or combinations of axial and rotational displacement) may also be used.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.